# Polyfills

The **Edge Runtime** is built on top of Web APIs available in Node.js.

The minimum Node.js version supported is **v14.6.0** that is mapped to **ES2019**.

Under the hood, the following Web APIs are used by the **Edge Runtime**:

| polyfill                                                                                                                                              | node14 | node16 | node18 |
| ----------------------------------------------------------------------------------------------------------------------------------------------------- | ------ | ------ | ------ |
| [util.types](https://github.com/vercel/edge-runtime/blob/main/packages/primitives/src/patches/util-types.js)                                          | x      |        |        |
| [WebCrypto](https://github.com/vercel/edge-runtime/blob/main/packages/primitives/src/primitives/crypto.js)                                            | x      |        |        |
| [AbortController, AbortSignal, DOMException](https://github.com/vercel/edge-runtime/blob/main/packages/primitives/src/primitives/abort-controller.js) | x      |        |        |
| [base64](https://github.com/vercel/edge-runtime/blob/main/packages/primitives/src/primitives/encoding.js)                                             | x      |        |        |
| [fetch, Request, Response](https://github.com/vercel/edge-runtime/blob/main/packages/primitives/src/primitives/fetch.js)                              | x      | x      |        |
| [URLPattern](https://github.com/vercel/edge-runtime/blob/main/packages/primitives/src/primitives/url.js)                                              | x      | x      | x      |
| [WebStreams](https://github.com/vercel/edge-runtime/blob/main/packages/primitives/src/primitives/streams.js)                                          | x      | x      | x      |

The Edge Runtime polyfills missing APIs for backward compatibility with older Node.js versions.

In the future, Node.js will become a superset of the Edge Runtime with built-in support for the [available APIs](/features/available-apis).
